// Captain Proto -- Protobuf Object-capability RPC
// Copyright (c) 2009 Kenton Varda, Google Inc., and contributors
// http://capnproto.googlecode.com
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of the Captain Proto project nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package capnproto;

import com.google.protobuf.ByteString;
import com.google.protobuf.InvalidProtocolBufferException;
import com.google.protobuf.MessageLite;
import com.google.protobuf.UninitializedMessageException;

public abstract class GeneratedChannel implements Channel {
  @Override
  public abstract <ResponseType extends MessageLite> ResponseType callMethod(
      String methodName, RpcContext context, MessageLite request,
      ResponseType responsePrototype) throws ServiceException;

  @Override
  public ByteString callMethod(String methodName, RpcContext context,
      ByteString request) throws ServiceException {
    PrototypePair prototypes = getPrototypes(methodName);

    MessageLite requestMessage;

    try {
      requestMessage =
        prototypes.request.newBuilderForType().mergeFrom(request).build();
    } catch (UninitializedMessageException e) {
      throw new ServiceException(
          "Request message invalid: " + e.getMessage(),
          Proto.CallError.Type.BAD_REQUEST, e);
    } catch (InvalidProtocolBufferException e) {
      throw new ServiceException(
          "Request message invalid: " + e.getMessage(),
          Proto.CallError.Type.BAD_REQUEST, e);
    }

    MessageLite responseMessage =
        callMethod(methodName, context, requestMessage, prototypes.response);
    return responseMessage.toByteString();
  }

  protected static final class PrototypePair {
    final MessageLite request;
    final MessageLite response;

    PrototypePair(MessageLite request, MessageLite response) {
      this.request = request;
      this.response = response;
    }
  }

  protected abstract PrototypePair getPrototypes(String methodName)
      throws ServiceException;

  @SuppressWarnings("unchecked")
  protected static <MessageType extends MessageLite> MessageType coerceType(
      MessageLite message, MessageType prototype)
      throws ServiceException {
    if (message.getDefaultInstanceForType() ==
        prototype.getDefaultInstanceForType()) {
      return (MessageType) message;
    } else {
      try {
        return (MessageType) prototype.newBuilderForType()
                                      .mergeFrom(message.toByteString())
                                      .build();
      } catch (UninitializedMessageException e) {
        throw new ServiceException(
            "Request message invalid: " + e.getMessage(),
            Proto.CallError.Type.BAD_REQUEST, e);
      } catch (InvalidProtocolBufferException e) {
        throw new ServiceException(
            "Request message invalid: " + e.getMessage(),
            Proto.CallError.Type.BAD_REQUEST, e);
      }
    }
  }
}
